Portable conveyor units are used for conveying bulk materials such as sand, gravel, concrete and the like. The typical portable conveyor unit includes an endless belt conveyor that is positioned at an inclined angle. The bulk material is fed to the lower end of the inclined conveyor and is discharged from the upper end through a hopper to a location of use.
To enable the conveyor unit to be readily moved between different locations on a given site, the conveyor is mounted on wheels. In the typical installation, a pair of rear wheels are located at the lower end of the conveyor, while a pair of caster wheels are supported from a horizontal axis through vertical pivot shafts and are located beneath the central portion of the conveyor.
To vary the angle of inclination of the conveyor, a pair of rear arms connect the axle to the rear or lower end of the conveyor while a pair of forward arms connect the axle to the forward or upper end of the conveyor. A cable mechanism is employed to pivot the forward arms relative to the rear arms to thereby change the angle of inclination of the conveyor.
With the portable conveyor unit as used in the past a change in inclination of the conveyor causes the caster wheel axle to rotate so that the pivot axes for the caster wheels are moved to a non-vertical position. The non-vertical attitude of the caster wheel pivot axes provides added stress on the axle and caster wheels supports and also makes the conveyor unit more difficult to move over the terrain.
Because of this, it has been the practice in the past to incorporate an axle leveling assembly with the conveyor unit. As the angularity of the conveyor is changed, the leveling assembly is manually operated to maintain the pivot axes of the caster wheels in a vertical attitude. In normal operation, two or three adjustments of the axle leveling assembly may be necessary as the conveyor is raised in order to maintain the pivot axes in a vertical position.
The incorporation of the axle-leveling assembly not only increases the overall cost of the conveyor, but the required adjustments of the assembly also increases the time required for elevating and lowering the conveyor.